A proposal to evaluate the utility and accuracy of emission tomographic techniques using single photon emitting radionuclides (not positron emitters) for quantification of myocardial infarct size. Two techniques will be evaluated: (1) Coded aperture imaging, and (2) emission computed tomography. The techniques will be used to image and quantify the uptake of an infarct-avid radiopharmaceutical (technetium-99m pyrophosphate) and a radiopharmaceutical which distributes in the heart proportional to myocardial perfusion (thallium-201 chloride). These techniques will be developed and their spatial and quantitative accuracy assessed in a quantifiable dog model for acute myocardial infarction and when possible, correlated with post-mortem measurements of infarct size and location.